As multimedia-based services are prevailing in the present computer environment owing to the progress of internet, the conventional file size for the service has become large.
Namely, high-speed data input/output (I/O) operations are essentially required to support a high-speed service for a large amount of data. A striping scheme is used at the system employing volume manager technique or RAID (Redundant Array of Inexpensive Disks) technique in order to provide a high-speed service.
In the striping scheme mentioned above, data is distributed across more than two disks and I/O operation is performed in a parallel manner for a better performance.
Also, in the file system area, since a file system may be located on a single disk (for example, when a volume manager or a RAID system is used, two or more disks are recognized as a single logical device to be recognized as a single device) and the data of each file may be scattered on the single disk, the size of a block, a fundamental unit in I/O operations, has been set large, focusing on how to locate data segments adjacent to one another, for an improved performance.
However, data is distributed according to a logical address in the striping scheme employing volume manager technique or RAID system technique, as illustrated in FIG. 1, which shows a striping scheme of a conventional volume manager.
Namely, the respective logical address blocks correspond sequentially to the respective blocks of the disk drives, for example, block-0 100, the first logical address block, to the first block 120 of disk-0 and the second block in the logical addresses to the first block of disk-1. In addition, several continuous blocks may be incorporated to a concept of an extent to enhance the I/O performance of a large capacity file.
FIG. 2 shows a conventional inode structure and a file data distribution on disks, wherein the inode structure comprises a header area 210 for storing file information and pointers 220 for a number of data blocks which store the file data.
Namely, with reference to FIG. 2, continuous logical blocks are not allocated to store the data of each file. The data of each file are dispersed across the whole logical volume. As a result, data can be maldistributed into a certain disk rather than being distributed evenly across the whole disks, which deteriorates file I/O performance.
Next, adjacent allocation of data blocks, which is introduced for effective I/O operation of high capacity files, e.g., multimedia files, in a file system, brings forth the same effect as the case of extents, instead of blocks, being used.
A prior art to the file level striping scheme is described in Korean Patent No. 10-1997-0072755 entitled to “Fast system reconstruction method in RAID level 5 system” registered on Dec. 23, 1997, U.S. Pat. No. 5,828,876 entitled to “File system for clustered processing system” registered on Oct. 27, 1998 and “A Persistent Snapshot Device Driver for Linux”, carried in 2001 Annual Linux Showcase/Usenix published on Nov. 6 to 10, 2001.
According to the above first prior art, data and parity blocks distributed across the whole disks are newly arranged to implement fast system reconfiguration in RAID level 5 system. According to the conventional method, the contents of the whole disks are read and then rewritten to the disks with a batch scheme, with the system operation intermitted.
Accordingly, the reconfiguration procedure caused a big overhead to the system performance due to the cost for the memory, which store the content of the related disk temporarily, and the time for performing a number of read/write operations.
Next, a file system for a clustered processing system is an effective file system that stores and retrieves data in a unix cluster computer system which includes a connection network for connecting processing nodes.
Namely, the improved file system is a data storing device, for example a disk device, connected to each processing node with a form of a shared SCSI device. The whole structure of the file system includes all the information needed for each processing unit to access the storing device.
The file system is divided into a super block area for managing the file system, an inode bitmap area, a revised journal area, an inode area, a data block bitmap area, and a data block area. The file system uses an interface with a distribution lock manager for controlling the use of the system.
Next, “A Persistent Snapshot Device Driver for Linux” provides online backup providing a persistent availability of data requested by a web server or a large capacity enterprise system. Moreover, the downtime of a system for performing the conventional offline backup can be prevented.
According to the paper, the snapshot technique, which supports online backup, provides a Linux-based device driver providing a permanent snapshot in a cluster circumstance; records metadata such as mapping blocks or modification blocks in a log disk; introduces a transaction identifier to overcome a system error in reflecting the log to the disk; and provides a lock manager for serializing the accesses to the metadata such as mapping information.
Even with the technologies of the prior patents, data for a specific file can still be maldistributed into a specific disk resulting in inefficiency in I/O operation.